Process of producing acetic acid.



Patented July 28, 1914.

E. H. FRENCH & J. R. WITHROW.

PROCESS 0F PRODUGINGAGETIG ACID.

'"" APPLICATION FILED JULY 9, 1909r 7 Siwa UNITED STATES PATENT OFFICE.

EDWARD H. lFRENCH, or DAYTON, AND JAMES ra. wrritnow, "or centramos., omo.

Specicaten'of Letters Patent.

Patented July 2B, 19714.

To zZZ 'whom it 'may concern:

Be -it known that we, EDWARD H. FRENCH and JAMES R. Y WiTHRoW, citizens of the pose of purifyingit; and consists in theV matters hereinafter described and out in the claims.

'lhe accompanying drawing illustrates partly in elevation and partly in section and somewhat conventionally the apparatus that can be used in carrying out the process.

Acetic acid, as at present produced, is made by treating acetate of lime with mineral acid and then distilling off the acetic acid with other volatile substances. Acetate of lime used in the process as heretofore commonly practised so far as we are aware was made by evaporating acetate liquors until they first become of a mushy Consistence, and then afterward drying the product on a hot floor or in a vacuum.' The acetic acid thus obtained contained pyroligneous and other impurities, which, according to .the old practice were removed by distilling it over a permanganate or a bi-chromate. p

It is generally known that when a sulfur acid, such as sulfuric acid, is added to acetate of lime for the production of acetic acid, the resulting distillate contains sulfur dioxid, pyroligneous impurities and other impurities. By our mesent process we propose to partially prevent the formation of these matters by subjecting the acetate of lime in a closed vessel, to a distilling heat preferably in a vacuum with agitation and then adding sulfuric acid to the still, preferably in the form of a spray to give an equal admixture throughout the mass. When this addition is accomplshedslowly and with a contemporaneous agitation together with a high vacuum, but little acid is lost through the decomposition of the sulfurie acid and subsequent formation of sulfur dioxid.

In carrying on our process we partially remove the impurities above mentioned by adding powdered or granular charcoal unpointed til the distillate becomes thoroughly blackened and blowing air through .the mixture. The probable action in this case s that the sulfur dioxid is in part.blowny out and part changed to sulfuric acid. We that charcoal h as greater absorptive capacity for wood oils "while the presence ,of air or other gas which is inert to vKittie acid. We then remove 4the ,charcoal by-'iltration or iecantation.l The liquid is then ,electrolyzed with a current of vs ueh 'amperage' as will pass lthrough the solution without volatiliz-ing the acetic acid, preferabl with sodium chlond 'or other salt, there y 'decomposing all remaining pyroligneous impurities and other foreign substances, such impurities and substances being removed and the acetic acid recovered by ordinary distillation. The amount of current used in any given case is immaterial and may be varied except if too much current is vused acid may be lost by vaporiza-t-ion or by decomposition into hydrocarbon and other undesirable bodies. On the other` hand with sol a small current the time of loperation is unduly prolongated. The point Where volatilization occurs varies with the quantity and character of the solution but such point' can easily be observed by those skilled in the art. f

We have discovered that the use of electrolysis directly to the distillate without the addition to it of other substances will urify the acetic acid, and we have also iscovered that the addition of salts, such as particularly specitied, greatly facilitates the electrolytic purification probably because of the chemical action of their nascent ions or components on the impurities in the acid.

In the accompanying drawing 1 designates the tank in which the distillate is treated with charcoal and an inert gas; 2 designates a spray device in the bottom of the tank for injecting the inert gas; 3 designates a` lter of ordinary construction arranged to receive the material from the tank l; the character 4 designates the tank having electrodes therein for electrolyti'- designates the still of ordinary construction used in distillation after the electrolytic treatment and 6 designates the condenser of the still.

The time consumed in the various. ste s herein described will vary according to t e .cally treatingthe liquor after filtration; 5 A

quantity treated but the completion of any particular step in any particular portion of A the process can be determined by the observation of the effects stated by those skilled in the art who are carrying it out.

A \What weclaim is:

1. The process of producing purified acetic acid directly from acetate of lime obtained in the destructive distillation of wood comprising in adding a mineral acid thereto, distilling off theY acetic acid and then subjecting the distillate to electrolysis maintained below the .terial decomposition o the acetic acid occurs to remove pyroligneous bodies and foreign volatile acids and oils.

2. The process of obtaining refined acetic acid directly comprising subjecting impure acetic acid to electrolysis maintained below the point at which material decomoint at which maposition of the acetic acid occurs to remove pyroligneous bodies `and foreign volatile acids and oils. 3. The process of obtaining refined aceti acid directly comprising subjecting impure acetic acid to electrolysis maintained below the point at which material decomposition of the aeeticacid occurs in conjunction with a salt to remove yroligneous bodies and foreign volatile aci s and oils.

' EDWARD H. FRENCH.

JAMES R. WITHROW.' lVitnesses to the signature of Edward H. French:

JOHN TROY, S. L. WINsLoW. Witnesses to the 4signature of James R. Withrow: y

BENJAMIN FINCKEL, GEORGE M. FrNcKEL. 

